new tax code K171 + underpaid £1721

ayupmeduck

So I am currently a student in my final year (feb start). I have 2 jobs currently with another I've just started which isn't on the HMRC site yet.
Job 1 - [2019] £5000 0TX | [2020] £5000 K171
Job 2 - [2019] £15000 1264TX | [2020] £15000 1264T
They are just estimates and I received £261 as a tax refund. Actual pay = job 1 - £1515, job 2 - £650
Next year estimate:

Your PAYE Income Tax estimate - 1815 Deductions [Underpayment from previous year] - £1721

Tax free allowance - £10922
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I am unsure why/how I have underpaid this current year?! I will no longer be doing job 1 from now on so the tax code shouldn't matter and from the looks of it job 2 is staying as 1264T so confused about the new tax allowance of £10922 from April

Dazed_and_C0nfused

Do you mean in total you will have had three different jobs in the current tax year and the taxable income from them so far is a grand total of £2,165 (£1,515 + £650)?

Ignoring small amount of interest have you had or do you expect to have any other taxable income in this tax year, 2019:20?

ayupmeduck

Dazed_and_C0nfused said:

Do you mean in total you will have had three different jobs in the current tax year and the taxable income from them so far is a grand total of £2,165 (£1,515 + £650)?

Ignoring small amount of interest have you had or do you expect to have any other taxable income in this tax year, 2019:20?

Sorry I am a student so no other taxable income.
Job one I shall be getting £0 this coming year. That is the one with tax code K171. Both jobs were bank contracts (zero contract hours).
Why/how have I underpaid by £1710?

Dazed_and_C0nfused

You probably haven't underpaid, it is likely just an estimate based on some changes to your tax codes through having multiple jobs.

If the very low tax code (K171) is for a job you're not expecting to get paid from in the next tax year I would say you are best waiting for your P60's for the current tax year and then ask HMRC to review your tax position for 2019:20 and if you don't owe anything then they remove that entry from your 2020:21 tax code.

All of the above assumes that the estimated £1,721 underpayment relates to 2019:20 and not a previous tax year (2018:19 or earlier).